Around 30,000 residents and visitors were ordered to evacuate a US island as Hurricane Earl approached.

Dare County issued the order for people in seven villages on Hatteras Island, on North Carolina's Outer Banks coastline. Only about 4,800 are permanent residents living from Rodanthe to Hatteras. Officials had earlier asked only visitors to leave.

County spokeswoman Dorothy Toolan said people who chose to stay were being advised they may go without government help and services for up to 72 hours after the hurricane passes.

Earl's strongest winds are expected to reach the coast in the early hours of Friday.

Holidaymakers along the dangerously-exposed Outer Banks took advantage of the typical picture-perfect day just before a hurricane arrives to pack their cars and flee inland, cutting short their summer just before the Labour Day three-day holiday weekend.

The governors of North Carolina, Virginia and Maryland declared states of emergency, sea turtle nests on one beach were scooped up and moved to safety, and the crew of the Navy's USS Cole rushed to get home to Norfolk, Virginia, on Wednesday, ahead of the bad weather. The destroyer was supposed to return later this week from a seven-month assignment fighting piracy off Somalia.

Further up the East Coast, emergency officials urged people to have disaster plans and supplies ready and considered whether to order evacuations as they watched the latest maps from the National Hurricane Centre - namely, the "cone of uncertainty" showing the broad path the storm could take.

Earl was expected to reach the North Carolina coast early on Friday, British time, and wheel to the north east, staying offshore while making its way up the Eastern Seaboard. But forecasters said it could move in closer, perhaps coming ashore in North Carolina, crossing New York's Long Island and passing over the Boston metropolitan area and Cape Cod.

That could make the difference between modestly wet and blustery weather on the one hand, and dangerous storm surge, heavy rain and hurricane-force winds on the other.

On Wednesday night Earl was a powerful Category 4 hurricane centred more than 680 miles south east of Cape Hatteras, North Carolina, with winds of 135mph.